Resource selection using a listen before talk procedure

Abstract

Wireless communications between a base station and one or more wireless devices are described. Multiple downlink reference signals may correspond to multiple random access resources for a random access procedure. A base station may provide a set of downlink reference signals before a set of physical random access channels (PRACHs) are available for use. A wireless device performing a random access procedure may select two or more random access resources (e.g., PRACH occasions) based on the downlink reference signals. Using a listen before talk (LBT) procedure, the wireless device may select a first available random access resource from the two or more random access resources that are determined to be clear.

What is claimed is: 
     
       1. A method comprising:
 receiving, by a wireless device, a plurality of downlink reference signals of a cell; 
 determining a first resource for random access, wherein the first resource is associated with a first downlink reference signal of the plurality of downlink reference signals of the cell; 
 determining, based on a failure of a first listen-before-talk (LBT) procedure, that the first resource is occupied; 
 determining, based on the failure of the first LBT procedure, a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and 
 based on a success of a second LBT procedure, transmitting, via the second resource, a preamble for a random access procedure. 
 
     
     
       2. The method of  claim 1 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
 a synchronization signal and physical broadcast channel block (SSB); or 
 a channel state information reference signal (CSI RS). 
 
     
     
       3. The method of  claim 1 , further comprising:
 receiving a radio resource control message indicating:
 that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and 
 a threshold value; and 
 
 selecting, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier. 
 
     
     
       4. The method of  claim 3 , wherein the selecting comprises one of:
 selecting the normal uplink carrier, based on the received signal strength being greater than the threshold value; or 
 selecting the supplementary uplink carrier, based on the received signal strength being less than or equal to the threshold value. 
 
     
     
       5. The method of  claim 1 , further comprising receiving a radio resource control message comprising beam failure recovery configuration parameters indicating:
 a candidate beam reference signal list, and 
 a preamble identifier of the preamble. 
 
     
     
       6. The method of  claim 1 , further comprising:
 determining that a first received signal strength of the first downlink reference signal and a second received signal strength of the second downlink reference signal are greater than a value. 
 
     
     
       7. The method of  claim 1 , wherein the first resource comprises a first physical random access channel resource and the second resource comprises a second physical random access channel resource. 
     
     
       8. The method of  claim 7 , wherein the first physical random access channel resource and the second physical random access channel resource are two different resources of a same physical random access channel. 
     
     
       9. A wireless device comprising:
 one or more processors; 
 memory storing instructions that, when executed by the one or more processors, configure the wireless device to:
 receive a plurality of downlink reference signals of a cell; 
 determine a first resource for random access, wherein the first resource is associated with a first downlink reference signal of the plurality of downlink reference signals of the cell; 
 determine, based on a failure of a first listen-before-talk (LBT) procedure, that the first resource is occupied; 
 determine, based on the failure of the first LBT procedure, a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and 
 based on a success of a second LBT procedure, transmit, via the second resource, a preamble for a random access procedure. 
 
 
     
     
       10. The wireless device of  claim 9 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
 a synchronization signal and physical broadcast channel block (SSB); or 
 a channel state information reference signal (CSI RS). 
 
     
     
       11. The wireless device of  claim 9 , wherein the instructions, when executed by the one or more processors, configure the wireless device to:
 receive a radio resource control message indicating:
 that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and 
 a threshold value; and 
 
 select, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier. 
 
     
     
       12. The wireless device of  claim 11 , wherein the instructions, when executed by the one or more processors, configure the wireless device to select the at least one of the normal uplink carrier or the supplementary uplink carrier by one of:
 selecting the normal uplink carrier, based on the received signal strength being greater than the threshold value; or 
 selecting the supplementary uplink carrier, based on the received signal strength being less than or equal to the threshold value. 
 
     
     
       13. The wireless device of  claim 9 , wherein the instructions, when executed by the one or more processors, configure the wireless device to:
 receive a radio resource control message comprising beam failure recovery configuration parameters indicating:
 a candidate beam reference signal list; and 
 a preamble identifier of the preamble. 
 
 
     
     
       14. The wireless device of  claim 9 , wherein the instructions, when executed by the one or more processors, configure the wireless device to:
 determine that a first received signal strength of the first downlink reference signal and a second received signal strength of the second downlink reference signal are greater than a value. 
 
     
     
       15. The wireless device of  claim 9 , wherein the first resource comprises a first physical random access channel resource and the second resource comprises a second physical random access channel resource. 
     
     
       16. The wireless device of  claim 15 , wherein the first physical random access channel resource and the second physical random access channel resource are two different resources of a same physical random access channel. 
     
     
       17. A system comprising:
 a wireless device; and 
 a base station,
 wherein the base station is configured to:
 transmit, to the wireless device, a plurality of downlink reference signals of a cell; and 
 
 wherein the wireless device is configured to:
 determine a first resource for random access, wherein the first resource is associated with a first downlink reference signal of the plurality of downlink reference signals of the cell; 
 determine, based on a failure of a first listen-before-talk (LBT) procedure, that the first resource is occupied; 
 determine, based on the failure of the first LBT procedure, a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and 
 based on a success of a second LBT procedure, transmit, via the second resource, a preamble for a random access procedure. 
 
 
 
     
     
       18. The system of  claim 17 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
 a synchronization signal and physical broadcast channel block (SSB); or 
 a channel state information reference signal (CSI RS). 
 
     
     
       19. The system of  claim 17 , wherein the wireless device is further configured to:
 receive a radio resource control message indicating:
 that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and 
 a threshold value; and 
 
 select, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier. 
 
     
     
       20. The system of  claim 19 , wherein the wireless device is further configured to select the at least one of the normal uplink carrier or the supplementary uplink carrier by one of:
 selecting the normal uplink carrier, based on the received signal strength being greater than the threshold value; or 
 selecting the supplementary uplink carrier, based on the received signal strength being less than or equal to the threshold value. 
 
     
     
       21. The system of  claim 17 , wherein the wireless device is further configured to:
 receive a radio resource control message comprising beam failure recovery configuration parameters indicating:
 a candidate beam reference signal list; and 
 a preamble identifier of the preamble. 
 
 
     
     
       22. The system of  claim 17 , wherein the wireless device is further configured to:
 determine that a first received signal strength of the first downlink reference signal and a second received signal strength of the second downlink reference signal are greater than a value. 
 
     
     
       23. The system of  claim 17 , wherein the first resource comprises a first physical random access channel resource and the second resource comprises a second physical random access channel resource. 
     
     
       24. The system of  claim 23 , wherein the first physical random access channel resource and the second physical random access channel resource are two different resources of a same physical random access channel. 
     
     
       25. A non-transitory computer-readable medium storing instructions that, when executed, configure a wireless device to:
 receive a plurality of downlink reference signals of a cell; 
 determine a first resource for random access, wherein the first resource is associated with a first downlink reference signal of the plurality of downlink reference signals of the cell; 
 determine, based on a failure of a first listen-before-talk (LBT) procedure, that the first resource is occupied; 
 determine, based on the failure of the first LBT procedure, a second resource for random access, wherein the second resource is associated with a second downlink reference signal of the plurality of downlink reference signals of the cell; and 
 based on a success of a second LBT procedure, transmit, via the second resource, a preamble for a random access procedure. 
 
     
     
       26. The non-transitory computer-readable medium of  claim 25 , wherein each of the plurality of downlink reference signals of the cell comprises at least one of:
 a synchronization signal and physical broadcast channel block (SSB); or 
 a channel state information reference signal (CSI RS). 
 
     
     
       27. The non-transitory computer-readable medium of  claim 25 , wherein the instructions, when executed, further configure the wireless device to:
 receive a radio resource control message indicating:
 that the cell comprises a downlink carrier, a normal uplink carrier, and a supplementary uplink carrier; and 
 a threshold value; and 
 
 select, based on a received signal strength of one of the plurality of downlink reference signals, at least one of the normal uplink carrier or the supplementary uplink carrier. 
 
     
     
       28. The non-transitory computer-readable medium of  claim 27 , wherein the instructions, when executed, configure the wireless device to select the at least one of the normal uplink carrier or the supplementary uplink carrier by one of:
 selecting the normal uplink carrier, based on the received signal strength being greater than the threshold value; or 
 selecting the supplementary uplink carrier, based on the received signal strength being less than or equal to the threshold value. 
 
     
     
       29. The non-transitory computer-readable medium of  claim 25 , wherein the instructions, when executed, configure the wireless device to:
 receive a radio resource control message comprising beam failure recovery configuration parameters indicating:
 a candidate beam reference signal list; and 
 a preamble identifier of the preamble. 
 
 
     
     
       30. The non-transitory computer-readable medium of  claim 25 , wherein the instructions, when executed, configure the wireless device to:
 determine that a first received signal strength of the first downlink reference signal and a second received signal strength of the second downlink reference signal are greater than a value. 
 
     
     
       31. The non-transitory computer-readable medium of  claim 25 , wherein the first resource comprises a first physical random access channel resource and the second resource comprises a second physical random access channel resource. 
     
     
       32. The non-transitory computer-readable medium of  claim 31 , wherein the first physical random access channel resource and the second physical random access channel resource are two different resources of a same physical random access channel. 
     
     
       33. The method of  claim 1 , wherein the determining the second resource comprises:
 triggering a random access resource selection procedure; and 
 determining, during the random access resource selection procedure, the second-resource.